Tutorial: "Understanding stacks" uses "project" without defining or linking it

[jkodroff]

Summary

The "Understanding stacks" tutorial introduces the term project without defining it or linking to the concept page. Surfaced via docs page feedback on 2025-12-30:

"The 'project' word is introduced without explaining what it is… is the project the same thing as the program, or is the project an instance of the program in Pulumi Cloud?"

Page: /tutorials/building-with-pulumi/understanding-stacks/ → source content/tutorials/building-with-pulumi/understanding-stacks/index.md

The gap

• "project" is used 5 times (lines 16, 20, 22, 24, 32) with no inline definition and no link.
• This is the first page (weight: 1) of the "Building with Pulumi" series, so the term appears undefined from the opening paragraph.
• Line 16 hand-waves with "as you've seen in previous tutorials" but provides no link.
• "project" is only defined one tutorial back, in Pulumi Fundamentals (content/tutorials/pulumi-fundamentals/create-a-pulumi-project/index.md:14-16), which is listed as a prereq. A reader landing here directly (e.g. via search) gets no definition anywhere in the 5-page series (confirmed: zero links to a project concept doc across the series).
• The Fundamentals definition itself conflates project ≈ program, which is the source of the user's exact project-vs-program ambiguity.

Canonical concept page to link

/docs/iac/concepts/projects/ (source content/docs/iac/concepts/projects/_index.md) — defines a project as "any folder that contains a Pulumi.yaml project file."

Suggested fix

Add a one-line gloss + link the first time "project" appears (line 16), mirroring the existing inline-definition-plus-link pattern already used for "stack"/"configurable" on line 14. For example:

A project — the directory containing your Pulumi.yaml and program — can have as many stacks as you need.

This also lets us drop the unlinked "as you've seen in previous tutorials" hand-wave.

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Verified via automated docs-feedback triage.